The primary goals of this research are i) to establish how learning impacts the structure and function of the brain, and ii) to determine how learning can be modulated by factors such as feedback (positive or negative). Over the past year we have focused equally on both of these goals. 1) Impact of learning on brain structure and function (Protocol 93-M-0170, NCT00001360) Over the past few years, we have been conducting a long-term longitudinal study of participants learning different tasks (e.g. motor sequences) to determine how structural properties of the brain (gray matter, white matter) change over time. Over a period of four weeks, participants were trained in two different tasks and we collected extensive functional and structural MRI data over the course of training. While previous studies have identified structural changes associated with learning, even over the course of a couple of hours, our initial findings have highlighted a potential confound that needs to be accounted for in such studies. Specifically, we have found that the structural measures obtained with MRI fluctuate according to the time of day with decreases in gray matter thickness and increases in ventricular volume that may reflect the impact of factors such as hydration level or factors associated with circadian rhythm. In ongoing work we are trying to establish what aditional structural and functional changes occur with training above and beyond these time-of-day effects. 2) Impact of feedback on learning (Protocol 93-M-0170, NCT00001360) We are investigating the impact of feedback (positive, negative) on motor learning. Groups of participants are trained on different motor tasks and either provided with positive, negative or neutral feedback. Training occurs in the MRI scanner and we are investigating the behavioral impact of feedback as well as changes in functional connectivity from pre- to post-learning and changes in activation over the course of the learning itself. Behaviorally, we find that the impact of feedback is dependent on the task. While in a sequence learning task we find that punishment improves online performance, we observe the opposite effct in a purely motoric force-tracking task. Establishing the nature, degree and consequences of plasticity in the adult cortex provides important insights into the potential for rehabilitative brain therapies following injury or dysfunction in the nervous system.